You can search for sandbars on this site and find a bunch of info. The most popular are in Braun Bay, behind Sleepers near West Alton Marina, near the cementary in Paugus Bay, and up near Center Harbor, I think it's called Patrician shores. There are tons of smaller ones and probably other that I don't know about.
I don't know what you have for a boat but I've seen these for several boats:
http://www.yamaha-motor.com/boat/acc...temdetail.aspx
As for bathrooms, you can always get one of these
http://www.westmarine.com/webapp/wcs...001/715/209/11
Or more likely, one of these:
http://www.westmarine.com/webapp/wcs...001/715/209/11